Field of the Invention (Technical Field)
The presently claimed invention relates to phototherapeutic treatment and more particularly to an apparatus, system, and method for phototherapeutic treatment of skin conditions and mood/sleep related disorders using light emitting diodes (LEDs).
Background Art
Exposure of the skin to lights having specific colors in the ultraviolet, visible, and/or near-infrared spectral ranges is a proven method for the treatment of a wide range of conditions. This method, also known as phototherapy, is being used successfully for treating skin conditions such as psoriasis as described in Ultraviolet Radiation Physics and the Skin, Diffey B L, Phys. Med. Biol. vol. 25 (3), pp. 405-426 (1980), acne vulgaris as described in Phototherapy with Blue (415 nm) and Red (660 nm) Light in the Treatment of Acne Vulgaris, Papageorgiou P, Katsambas A, Chu A, British Journal of Dermatology, vol. 142(5), pp. 973-978 (2002) (hereinafter Papageorgiou), vitiligo as described in A Retrospective Study of Narrowband-UVB Phototherapy for Treatment of Vitiligo in Malaysian Patients, Adauwiyah J, Suraiya H H, Med. J. Malaysia 65(4), pp. 297-299 (December 2010), as well as treating various seasonal affective disorders as described in Influence of a Mindfulness Meditation-Based Stress Reduction Intervention on Rates of Skin Clearing in Patients With Moderate to Severe Psoriasis Undergoing and Phototherapy (UVB) and Photochemotherapy (PUVA), Kabat-Zinn J, Wheeler E, Light T, Skillings A, Scharf M J, Cropley T G, Hosmer D, Bernhard J D, Psychosom. Med., vol. 60, pp. 625-632 (1998). Phototherapy is often indicated for the treatment of neonatal jaundice as disclosed in Numbers Needed to Treat with Phototherapy According to American Academy of Pediatrics Guidelines, Newman T B, Kuzniewicz M W, Liljestrand P, Wi S, McCulloch C, Escobar, G J Pediatrics, vol. 23 (5), pp. 1352-1359 (May 2009) and in supporting wound healing as described in Light Therapy and Advanced Wound Care for a Neuropathic Plantar Ulcer on a Charcot Foot, Sutterfield R, J Wound Ostomy Continence Nurs., vol. 35(1), pp. 113-115 (January-February 2008). Phototherapy has also been shown to be beneficial for reducing undesired pigmentation as disclosed in U.S. Pat. No. 6,991,644, entitled Method and System for Controlled Spatially-Selected Epidermal Pigmentation Phototherapy with UVA Leds, to Spooner, et al., (Jan. 31, 2006), and supporting skin rejuvenation by increasing the amounts of collagen and elastic fibers, as described in A Prospective, Randomized, Placebo-Controlled, Double-Blinded, and Split-Face Clinical Study on LED Phototherapy for Skin Rejuvenation: Clinical, Profilometric, Histologic, Ultrastructural, and Biochemical Evaluations and Comparison of Three Different Treatment Settings, Lee S Y, Park K H, Choi J W, Kwon J K, Lee D R, Shin M S, Lee J S, You C E, Park M Y, J. Photochem and Phtobio. B: Biology, vol. 88(1), pp. 51-67 (2007), hereinafter (Lee).
Specific colors of light are particularly effective for treating certain conditions. For example, light having primary wavelengths of 633 nm (red) and 830 nm (near-infrared) is effective for collagen and elastic fiber production in skin rejuvenation, as discussed in Lee. Light of 700 nm (near-infrared) and 530 nm (green) wavelengths can increase fibroblasts for accelerated wound healing as described in Effect of LED Phototherapy of Three Distinct Wavelengths on Fibroblasts on Wound Healing: A Histological Study in a Rodent Model, Cavalcanti de Sousa A P, Santos J N, dos Reis Jr. J A, Ramos T A, de Sousa J, Cangussu M C T, Pinheiro A L B, Photomed and Laser Surgery, vol. 28(4), pp. 547-552 (2010) and light of 415 nm (blue) and 660 nm (red) is effective in supporting the treatment of acne vulgaris as discussed in Papageorgiou.
LEDs are a cost-effective means of producing the desired wavelengths, the relatively narrow spectral power distributions, and the relatively low optical power levels desired for phototherapy. A phototherapy device incorporating a plurality of LEDs with different colors is particularly attractive and can be used for the treatment of multiple conditions. Uniform illumination of the skin is essential for the treatment of skin conditions to ensure an unvarying stimulation of the treatment area. Furthermore, the light emitted by the LEDs should reach the treatment area in order to maximize the illumination efficiency, thus, allowing the use of fewer and/or lower-power LEDs.
LEDs are incoherent light sources that emit light with a wide angular (Lambertian) distribution compared to lasers that emit a narrow beam of light. Lenses (primary optics) are often directly integrated with the LED chip into a single package in order to redirect most of the LED chip light output into a relatively narrow cone in the forward direction.
Ideally, an LED phototherapy device uses all the emitted light to illuminate the subject's skin treatment area in a uniform manner. In order for the device to be cost-effective and produce a high quality light for phototherapeutic applications, both high illumination uniformity and high illumination efficiency are necessary. However, these two properties tend to be mutually exclusive because of the inherent divergence of the LED output. For example, at a substantial distance between an LED array and a subject (e.g. >0.5 foot), the illumination uniformity is generally high because the diverging light output of the individual LEDs overlap. However, the efficiency is low because much of the emitted light misses the subject's treatment area. In contrast, the illumination efficiency is high at a close distance (e.g. <0.5 foot) where the LED array is “near the skin” of the subject; in this case, the illumination is non-uniform because of reduced overlap of the diverging LED outputs.
Non-uniform illumination of the skin treatment area is not desirable. However, when using LEDs with different colors and intensities arranged on a panel, it is difficult to obtain a uniform illumination of a given treatment area in close proximity. This is because lensed LEDs are substantially point-like light sources that typically emit light into a relatively narrow forward cone. Yet close proximity of the LED array to the skin is preferable in order to make best use of the emitted light (high illumination efficiency).
FIGS. 1A through 1F illustrate the problem. These figures represent the calculated illumination of a fixed-area target surface placed parallel to a LED array at different distances. The representative arrangement in this example comprises 22 LEDs with a divergence of ±15° and placed on a 10×7 rectangular grid with a LED spacing of 17.8 mm and 21.5 mm in the horizontal and vertical directions, respectively. FIG. 1A shows the efficiency of 99.0% at 1 inch, FIG. 1B shows the efficiency of 90.0% at 3 inches, FIG. 1C shows the efficiency of 79.5% at 6 inches, FIG. 1D shows the efficiency of 62.0% at 12 inches, FIG. 1 E shows the efficiency of 39.7% at 24 inches, and FIG. 1F shows the efficiency of 21.8% at 48 inches. For example, the spatial intensity distribution on a target surface (fixed area) in close proximity (1 inch) and parallel to a planar array of LEDs is highly non-uniform (FIG. 1A). Moving the target surface away from the LED array (FIGS. 1B-F) improves the spatial intensity distribution due to the greater spatial overlap of the diverging LED outputs; however, it comes at the expense of a reduced irradiance of the target surface as much of the light misses the target surface due to divergence. Space constraints further exacerbate the problem when an array of LEDs with several different colors is used and uniform illumination of the target area for each of those colors is preferable. Given a certain number of LEDs, the challenge is to find an LED arrangement and device design that gives both high illumination uniformity and high illumination efficiency.
Existing systems have the LEDs in rows or arranged for ease of manufacturing, but not based on optimal performance for the skin. Some systems require the user to move the device across the skin manually in an attempt to illuminate, uniformly all portions of the treatment area. Other devices require the user to lay stationary and move the LED panel to achieve uniform illumination; and still other devices use a large number of LEDs with the subject at a significant distance to achieve uniform illumination. These complexities and associated costs often limit existing devices to only one or two colors.
Several prior art approaches (and combinations of those) have been used in an attempt to solve the problem of achieving uniform and efficient illumination of a subject's skin.
Some devices are intended for use at a relatively large distance between the LED panel and the subject. At the large distance, the outputs of the individual LEDs mix well and produce a favorable, uniform illumination. An example of this approach is a LED panel described in U.S. Pat. No. 6,896,693 that is intended to be used at distances greater than 6 inches and up to several feet.
Other devices use a linear array of LEDs mounted in rows on an arm structure that moves back and forth on a semicircle with the subject stationary at the center of the arc. This can be combined with a relatively large distance (>6 inches) between the LEDs and the subject. The motion of the LEDs relative to the stationary subject and the distance creates a substantially uniform illumination of the subject's skin. An example is the MAX device marketed by MAX LED Technologies (Montreal, Quebec; http://www.maxledtechnologies.com). Another example are small handheld LED devices that have to be moved around the subject's skin like the ones marketed by Sirius Beauty (http://www.siriusbeauty.com), Bright Therapy (http://brighttherapy.com/acne-lamp-led-green-red-blue-infrared-led-cluster-with-3-detachable-treatment-heads.html), LightStim (http://www.lightstim.com), and many others. It is time consuming and tiring to use a small handheld device to cover large areas of the body, thus, making it less likely to sustain consistent use by the consumer.
Some devices use a large number of LEDs of a single color in the panel. Increasing the number of LEDs increases the spatial overlap of their outputs and produces a substantially uniform illumination. An example is the device marketed by Omnilux (http://www.omnilux.co.uk).
Other devices use secondary optics such as light guides and transmissive diffusers placed between the LED sources and the target area in order to achieve a substantially uniform illumination. Examples are U.S. Pat. Nos. 7,077,544 and 5,876,107 in which a transparent member (light guide) is used in conjunction with a LED source. Another example is a device marketed by Beauty Essence Co. that uses intricate mirror-like reflectors around each LED (http://www.amazon.com/Charming-Foldable-Machine-Rejuvenation-Dynamic/dp/B008X0WEUI/ref=sr_1_1?s=hpc&ie=UTF8&qid=1398647823&sr=1-1).
Some devices use a non-uniform spatial distribution of the LEDs in an array, optionally combined with individually adjusted LED intensities to achieve a substantially uniform illumination of a target surface. An example is U.S. Pat. No. 7,131,990.
In general, the above prior art approaches have a small treatment area and/or only a few (typically 1 or 2) colors. Most systems have non-uniform illumination, and some have complex moving parts. All these disadvantages make these devices less user-friendly and effective for the consumer.
The specific drawbacks of the above-described approaches are:                Relatively large distance: The drawback is that much of the emitted, highly divergent light does not reach the subject's skin and the irradiance is low, resulting in reduced phototherapeutic effects.        Motion of the LEDs: The disadvantage is that the device is larger and more complex/costly (compared to a device with stationary LEDs) because of the motion apparatus. In addition, the relatively large distance between the LEDs and the subject reduces the effective irradiance.        Large number of LEDs: The disadvantage is that the large number of LEDs comes at increased cost and power consumption. Furthermore, such devices often use only one or two therapeutic colors due to space/cost constraints.        Secondary optics: The disadvantage is that the added optical elements can make the device bulky, heavier, less efficient, and more expensive.        Non-uniform spatial distribution of the LEDs: There are infinite numbers of possibilities to arrange LEDs non-uniformly on a panel. Different arrangements produce different degrees of illumination uniformity. Non-uniform arrangement of LEDs is an effective way to achieve uniform illumination, and it is used in the presently claimed invention; however, the LED arrangement is paramount to the efficiency of the system.        
Several units provide LED light therapy to the consumer, but in various other forms. Some are small, round or triangular shaped heads containing ˜30 LEDs integrated into a handle; others are panels that contain one or two colors in various configurations; even others, as a bendable pad or a single panel. None achieves substantial, uniform illumination for four colors.
While arrangements of LEDs on arrays that achieve uniform illumination of a target area have been described, those arrangements typically follow simple and often symmetric patterns (such as alternating two colors on a grid). With multiple colors of LEDs having different light intensities for each color and a given number of LEDs in each color (to achieve the desired overall optical power level in each color), especially for three or more colors, it is not obvious how to best arrange the LEDs so that each emission color achieves the best possible illumination uniformity and illumination efficiency of a target surface. The computational method disclosed herein is an efficient way to identify LED arrangements that offer the desired properties. A given light intensity per color can be obtained for any number of colors with optimized light output uniformity on a given target.
Therefore, there is a need for a LED phototherapy device that has a plurality of colors, achieves a substantially uniform illumination for each color over a treatment area in close proximity without the need for moving the device, and is cost effective.